So I've decided I want to dirt my 15 gallon once I figure out where to put it. I'm wondering if I should use miracle grow or mineralized topsoil? If I use miracle grow do I mineralize that too? I would like to avoid worrying about ammonia from the soil, mineralizing seems to be safer. Do I do 1.5 inch each of dirt and sand? Are there any issues with the substrate becoming anaerobic? I'm going for a low tech moderate to heavily planted tank.